Munition guidance systems have evolved considerably since the initial introduction of heat-seeking missiles in the late 1950's. Missiles, rockets, and other munitions are now commonly equipped with advanced homing guidance systems referred to as “seekers.” Modern seekers often include two or three independent detector subsystems, which each support a different guidance modality. These detector subsystems are independent in the sense that each subsystem includes at least one dedicated electro-optic sensor (e.g., a detector array sensitive to wavelengths in the visible or infrared spectrum) positioned within a distinct focal plane. Additionally, each detector subsystem typically includes a separate, dedicated processor, which processes signals provided by the subsystem's detector array indicative of registered electromagnetic energy. Each detector subsystem then supplies this data to a main navigational computer (commonly referred to as the “mission computer”) deployed onboard the guided munition. The navigational computer utilizes the data supplied by the seeker subsystems, often in combination with data generated by other systems deployed onboard the munition (e.g., a global positioning system and an inertial navigational system) and possibly telemetry data provided by external control sources, to determine the manner in which one or more flight control surfaces should be manipulated to provide aerodynamic guidance to the munition during flight.
The independent guidance systems employed by dual- and tri-mode seekers commonly include separate infrared imaging and Semi-Active Laser (“SAL”) subsystems. Conventionally-implemented infrared imaging systems often include a detector array containing a relatively high number of detector cells (e.g., a 640×480 cell grid) fabricated from a detector material (e.g., HgCdTe and InSB) sensitive to infrared energy within the thermal bands (i.e., mid- to long-wave infrared energy). A single read-out integrated circuit is positioned behind the detector array and, during seeker operation, transmits signals indicative of the irradiance received across the detector array to a dedicated imaging processor. The processor then compiles the irradiance data to produce a composite intensity image of the seeker's field-of-view, which is supplied to the munition's main navigational computer for image-based guidance purposes. By comparison, a conventionally-implemented SAL subsystem typically includes a separate detector array comprised of a relatively small number of detector cells (e.g., four wedge-shaped cells, which collectively form a four-quadrant circular detector array). Analog circuitry operably coupled to each of the detector cells detects photocurrents induced by photons striking the detector array and supplies corresponding signals to a dedicated temporal processor. The temporal processor then compares intensity ratios across the detector cells to determine the centroid of any detected laser spot, which is provided to the main navigational computer as line-of-sight guidance data.
There is a continual demand to reduce the complexity, part count, weight, envelope, and cost of the various components (e.g., optical components, sensors, digital and analog processing elements, etc.) included within multi-mode seekers while maintaining or improving the seeker's guidance capabilities. More specifically, there exists an ongoing need to provide embodiments of a multi-mode seeker that reliably provides both imaging and Semi-Active Laser guidance capabilities with fewer components, with an enhanced reliability, and with an improved accuracy. Embodiments of such a multi-mode seeker are provided herein. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and this Background.